Systems that support a driver to perform safe driving and rapidly perform emergency measures in emergency by providing to the driver information on air pressure in a tire while travelling through diagnosis of a tire condition like a tire pressure monitoring system (TPMS) of a vehicle have been developed to provide a function for acquiring sensor information of various wireless sensor networks in addition to the TPMS. However, since supply power is used up depending on the use of a secondary battery and thereafter, a need for battery replacement through manpower allocation, troublousness and temporal and economical losses are generated at all times. Further, it is very important to select a light element due to problems caused by deposition of piezoelectric materials and an increase in volume in order to improve an output of a piezoelectric power generating element.
As seen in the example of the TPMS, the development of a system which a TPMS module installed in an aluminum wheel in the tire can transmit and receive a target to be determined, that is, information on a space to and from has been extremely required. In addition, in configuring the wireless sensor network, sensor components have been light-weight and small-sized due to the development of MEMS elements that take charge of several functions and as the piezoelectric power generating element that is developed as a substitution for the secondary battery, a bulk piezoelectric body has been currently used. In the future, in addition to the needs for thinning elements, an importance of the technological development to self-supply a power required to operate a sensor has been significantly emphasized. Further, the TPMS which is once mounted on the tire of the vehicle requires a life-span of 10 years or more and in addition, a concern about not the existing battery but an element capable of generating electricity by using a physical quantity of a wire environment, that is, vibration or an air pressure change in the tire has been further heightened.
As a fundamental solution for operating a sensor module without the battery in operating a sensor or actuator module under various environments of various places, the development of a self-powering power generating element has still be left as an assignment and researchers are researching the wind, the sun, and vibrations as energy sources thereof. A system, should be developed, which can provide environments and situational judgment information, which are more helpful to us by supplying energy required for the sensor module adopted in the wireless sensor network based on the physical quantities to further extend operating hours of the sensors.
The tire continuously rotates while travelling and in this case, the piezoelectric power generating element also rotates simultaneously. In this case, in the case of a heavy mass body, the mass body may be inclined to one side by centrifugal force rather than a vertical vibration quantity and the thinning technology of the piezoelectric power generating element is a current technological assignment that the researchers should solve surely.
In the related art, under the background of the research needs, an electricity generating element of a unit element level or an element supplying generated power by arranging a plurality of same elements and research results fabricated in a bulk type are present. Further, in order to complement a demerit in which an output of the unit element level is low, an array type or stack type technology is researched and developed. However, for now, due to a technological problem in which an output power of the power supply element should be further increased, if the volume is continuously increased, there is a very high possibility that a function as a power generating element regardless of the centrifugal force of a rotator will be lost.